1. Field of the Invention
The invention relates to a power tool and more particularly, to a power tool which can regulate internal pressure of a housing space for a driving mechanism.
2. Description of the Related Art
An electric hammer is known including a driving mechanism housed within a housing and driven by a motor to drive a tool bit for performing a striking movement in its axial direction and a rotation in its circumferential direction. Lubricant such as grease for lubricating the driving mechanism is provided within the housing space that houses the driving mechanism. The housing space is enclosed for preventing the charged lubricant from leaking to the outside. In such a construction, when the known hammer is operated, air within the housing is heated by an operation of the driving mechanism, such that the air within the housing expands to increase inside pressure. As a result, lubricant may possibly leak from the housing to the outside.
In this respect, Japanese laid-open Patent Publication No. 2008-36754 discloses an electric hammer which is capable of regulating the pressure of the housing space. According to this electric hammer, a pressure regulating path is formed by a filter chamber, an inner passage that communicates the filter chamber with the housing space of the housing, and an outer passage that communicates the filter chamber with the outside. Further, a filter is disposed in the filter chamber and spaced apart from a peripheral edge of an opening of the outer passage which is open to the filter chamber, so that lubricant within the housing space can be prevented from leaking to the outside.
While the above-described known art prevents leakage of lubricant from the housing space, further improvement is desired.